Constructor
is a special method of a class which will invoke automatically whenever
instance or object of class is created. Constructors are responsible for object
initialization and memory allocation of its class. If we create any class
without constructor, the compiler will automatically create one default
constructor for that class. There is always at least one constructor in every
class. If you want to know more about constructors check this article constructors
in c#.

Private Constructor

Private
constructor is a special instance constructor used in a class that contains
static member only. If a class has one or more private constructor and no
public constructor then other classes is not allowed to create instance of this
class this mean we can neither create the object of the class nor it can be
inherit by other class. The main purpose of creating private constructor is
used to restrict the class from being instantiated when it contains every
member as static.

using System;

namespace ConsoleApplication3

{

publicclassSample

{

publicstring
param1, param2;

public Sample(string
a,string b)

{

param1 = a;

param2 = b;

}

private Sample()
// Private Constructor Declaration

{

Console.WriteLine("Private
Constructor with no prameters");

}

}

classProgram

{

staticvoid Main(string[] args)

{

// Here we don't have chance to
create instace for private constructor

Sample obj = newSample("Welcome","to Aspdotnet-Suresh");

Console.WriteLine(obj.param1 +" " + obj.param2);

Console.ReadLine();

}

}

}

Output

Welcome
to Aspdotnet-Suresh

In above method we can create object of class with
parameters will work fine. If create object of class without parameters it will
not allow us create.

// it will works fine

Sample obj = newSample("Welcome","to Aspdotnet-Suresh");

// it will not work because of
inaccessability

Sample obj=newSample();

Important
points of private constructor

-One use of private construct is when we
have only static member.

-Once we provide a constructor that is
either private or public or any, the compiler will not allow us to add public
constructor without parameters to the class.

-If we want to create object of class even
if we have private constructors then we need to have public constructor along
with private constructor

I
hope it helps to know about private constructor. If you want to know more about
constructors check this article constructors
in c#.

the main use of private constructor is that when we use utility or resource file in our project that time just call that class without instanciating or inherting to save the memory reserve and faster access.